1. Field of the Invention
The present invention relates to an antenna for use in the field of telecommunications.
2. Description of the Prior Art
It is a recognized fact that the development of telecommunications and in particular satellite communications (data reception and transmission, TV reception) calls for the use of antennas having increasingly sophisticated radio-propagation performances as well as mechanical performances. Nevertheless, the constant upward trend in the number of potential users is an incentive to the design of products which remain at low cost levels while at the same time achieving very high standards of efficiency.
Conventional antennas of the reflector type either have a paraboloidal structure (paraboloid of revolution) or an offset structure.
The paraboloidal antenna has the advantage of high polarization purity. However, the existence of aperture blocking by the radiation source, or so-called feed, essentially impairs the radiation efficiency and radiation diagrams.
The offset-structure antenna offers the advantage of freedom from aperture blocking by the feed but suffers, however, from low polarization purity.
These antennas are associated with standard mounts which can be either of the XY type or of the azimuth-elevation type (az-el mounts).
The main drawback of the XY mount lies in the absence of a vertical axis which makes it necessary for the operator to carry out conversions in order to change over to local references (horizontal and vertical references of the installation site location). This type of mount calls in addition for the use of conversion tables, which is liable to carry the penalty of a longer installation time.
Mounts f the az-el type having a vertical axis have an advantage in that the azimuth and elevation adjustments can be made independent of each other (the azimuth being expressed with reference to the geographic or magnetic north and the elevation being expressed with reference to the horizontal axis of the site location).
Antenna mounts at present available commercially (carrousel, barrel, tripod) are often complex and costly to construct.